Tuesday, December 03, 2013

Last month we blogged about how regenerative braking might be possible for electric bicycles. Using a crude estimation, we estimated that regenerative braking alone would have a difficult time re-charging the e-bike’s batteries enough to boost a cyclist to high speeds or up hill.

It looks like MIT in collaboration with the Cambridge-based startup Superpedestrian have solved the problem because today they announced that their latest product, the Copenhagen Wheel, is now available for pre-order. Since it was founded in late 2012, Superpedestrian has been working toward untangling the knots and finer details in order to commercialize the Copenhagen Wheel – an MIT design that transforms regular bikes into e-bikes.

The Copenhagen Wheel has now joined the burgeoning e-bike market. What makes it unique, and might give it a competitive edge, is its versatility.
Buy a traditional e-bike online, and you’ll likely spend thousands of dollars for a rather heavy bicycle that will motor you from place to place – as long as the batteries are charged.

Instead of a bike, the Copenhagen Wheel is a wheel with a built-in motor that you attach to a regular bike. In place of the rear bike wheel is the Copenhagen Wheel. One of its main selling points is its regenerative braking feature.

The Copenhagen Wheel, like any electric bicycle, uses batteries to give the rider an extra boost. Regenerative braking is a natural way the rider can recharge the batteries so they last longer. This reduces the need for expensive portable battery charge packs and not-always-convenient electric outlets.

“The average non-professional rider puts out around 75 watts [when riding],” MIT researcher and founder of Superpedestrian Assaf Biderman told Boston Magazine when describing the startup’s new product. “With the motor you get a continuous 250 watts extra. That’s 325 watts. That’s more than four times than your average person can put out. You are almost four times stronger.”

This is assuming that the biker is putting energy into the bike by pedaling. Traditional e-bikes can be significantly heavier than regular bikes, weighing as much as 40 pounds, making them hard to ride without the motor’s aid.

The Copenhagen Wheel weighs 12-pounds and, while not an insignificant amount, provides a lighter e-bike alternative. Therefore, the idea is certainly plausible that a cyclist could pedal a bike with a Copenhagen Wheel with and even without the aid of the motor inside its engine-red encasing.

Moreover, the fact that your money is going toward purchasing a wheel as opposed to a bike with all the bells and whistles, the Copenhagen Wheel is notably less expensive than traditional e-bikes. If you’re one of the first 1000 customers to pre-order, you can purchase the Copenhagen Wheel for $700.

Whether the Copenhagen Wheel proves to be as efficient as traditional e-bike models remains to be seen. There are still questions that need answering in order to assess the investment value of the wheel:

How quickly will the motor expend its batteries when going up hill or moving against a strong wind?

How much energy can the wheel’s regenerative braking feature actually store?

What’s the average lifetime of the batteries and is 250 watts the maximum energy they can store?

How much energy must a motor put out to make a cyclist feel like they’re pedaling on flat ground while in reality they're traveling up hill, as the wheel’s advertisement suggests is possible? And is this energy less, the same or more than the max energy the batteries can store?

Type of terrain is a major factor in how efficient regenerative braking can work. For this reason, should only people in certain regions purchase the wheel?

Most likely, the engineers at MIT have considered these questions. But what are the answers and what do they mean for how competitive the Copenhagen Wheel will be in the e-bike market five, ten or fifteen years from now?

The specs for the money look OK. However, don't expect this setup to take you far up a mountain. It's nice that you might recover some of your effort on the downhill side, but it will be a real chore getting it to the top, especially in a headwind with a large rider on the bike.

We give power requirements here: http://www.evsroll.com/Electric_Assisted_Bicycles.html